Chain jack

ABSTRACT

A chain jack is operated by alternately transferring the chain load from a cylinder or base latch mechanism to a ram head latch mechanism and moving the base and the ram head away from and toward each other by alternate extension and retraction of the ram to cause relative movement between the chain and the base. The chain load is sequentially supported first by one latch and then the other; one latch cannot be disengaged from the chain unless the other is supporting the load. Actuation of the latches is controlled by hydraulic connection to valves operated by cams and followers in a side arm and fixed element arrangement whose relative movement is synchronized with movement between the base and the ram to control high pressure liquid flow to latch actuating hydraulic cylinders.

United States Patent 1191 Chambers Jan. 14, 1975 CHAIN JACK [75] Inventor: Henry B. Chambers, Santa Inez,

Calif.

[73] Assignee: Hydranautics, Goleta, Calif.

[22] Filed: Dec. 4, 1972 21 Appl. No.: 312,024

52 US. Cl. 254/110, 254/93 R 51 1111.01 .,B66i1/00 [58] Field of Search 254/105-111,

[56] References Cited 9 v UNITED STATES PATENTS 7 2,973,566 3/1961 Elsner 254/93 R 2,996,284 8/1961 Welborn 3,361,035 1/1968 Rountree 3,499,629 3/1970 Horton 254/93 R Primary Examiner-Al Lawrence Smith Assistant Examiner-Robert G. Watson Attorney, Agent, or Firm-Clement H. Allen [5 7] ABSTRACT A chain jack is operated by alternately transferring the 1 chain load from a cylinder. or base latch mechanism to a ram head latch mechanism and moving the base and the ram head away from and toward each other by alternate extension and retraction of the ram to cause relative movement betweenthe chain and the base.

The chain load is sequentially supported first by one latch and then the other; one latch cannot be disengaged from the chain unless the other is supporting the load. Actuation of the latches is controlled byhy- 1 draulic connection to valves operated by cams and followers in a side arm and fixed element arrangement whose, relative movement is synchronized with movement between the base and the ram to control high pressure liquid flow to latch actuating hydraulic cylinders.

7 Claims, 6 Drawing Figures CHAIN JACK BACKGROUND OF THE INVENTION 1. Field of the invention This invention relates to an improved chain jack.

2. The prior art Chain jacks are used often in marine, shipbuilding and construction operations to lift heavy loads precisely and economically. They generally comprise a hydraulic cylinder or base having a piston or ram attached to a head. Movable latches are attached to, or made as parts of, the base and head, each of which engages a chain between links thereof, actuation of these latches being controlled so that they move alternately in and out of engagement with the chain links as the ram moves in and out of the hydraulic cylinder. The load is sequentially supported by one latch and then the other. Conveniently, the hydraulic cylinder may extend the ram at each stroke a length nominally equivalent to one pitch of the chain. The latch at the ram head will be engaged with the chain during piston extension while the base latch will be released. When the piston has reached the end of its stroke, the base latch engages the chain and the ram head latch is released while the ram retracts. Then the ram head latch is engaged with the chain and the base latch released again and the cycle repeated to advance the chain for another short distance.

Since chain jacks are most often employed for handling heavy loads, construction of their parts and components must be correspondingly heavy. The latches employed must be strong enough to support the load carried by the jack and to obtain this strength the thickness of the latch may take up almost all the available space or window between adjacent chain links lying in the same plane. Therefore, very close control of latch actuation is necessary so that each latch enters into engagement and is released from the chain at exactly the proper position of the chain with respect to the cylinder or base and the head of the ram. This invention provides latch actuation control synchronized with the ram head movement, and one latch cannot be disengaged unless the other is supporting the load. Additionally, this invention provides precise control of latch entry into each window between links, even when this window is only a small amount wider than the thickness of the latch.

BRIEF SUMMARY OF THE INVENTION Summarized briefly, this invention comprises a chain jack having a chain, a base, and a ram with movable latches attached to the base and to the ram head. The base and the ram head are moved repetitively with respect to each other while the latches are actuated in and out of engagement with the chain, synchronized with the relative movement between the base and the ram head to cause relative movement between the base and the chain. The means for controlling the latches comprise a side arm attached to either one of the ram head or the base, and a fixed member attached to the other. The side arm slides by the fixed member to enable cooperation between these elements, which is synchronized with the relative movement between the base and the ram head. Preferably, the side arm is provided with longitudinal grooves to form cams which act on followers movably mounted on the fixed member and which are connected to hydraulic latch actuating positions'of the fixed member and the side arm. The

grooves or cams on the side arm are so arranged along the side arm to actuate the latches only when a window or space between links is presented, or about to be presented, so that accurate engagement at the proper position is obtained. Preferably, the latch about to enter into engagement with the chain is urged or biased to enter at a position prior to the actual entry position ating force, conveniently obtained by use of conven tional hydraulic cylinders, of relatively low magnitude, I

so that it will push an engaging latchinto engagement by following around a link, and will not be strong enough to disengage a latch while it is carrying the chain load, but will operate immediately the load is released.

BRIEF DESCRIPTION OF THE DRAWINGS Construction and operation of this invention will be apparent from the followingdescription thereof andfrom the annexed drawings in which:

FIG. 1 shows a vertical side view of a chain jack embodying features of this invention.

FIG. 2 shows a side view of the chain jack of FIG. 1 from a position from FIG. 1 with partsbroken out to show vertical central sections.

FIG. 3 shows a top view of the chain jack of FIG. 1.

FIG. 4 is a detailed enlarged side view of the side arm cam element configuration for lift" mode.

FIG. 5 is a detailed enlarged side view of the side arm cam element configuration from a position 90 from FIG. 4 for lower mode.

FIG. 6 is a vertical cross section of the cam element of FIG. 4 taken along the line 6-6.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring more particularly to FIGS. 1 and 2, the chain jack comprises a base 10 to which is fixedly attached the bottom ends of inner cylinder 12 and outer cylinder 14. In the annular space between cylinders 12 and 14 rides a piston 16 attached to ram 18 at the outer end of which is attached ram head 20. Piston I6 is sealed to the inner surface of outer cylinder 14 by sliding seals 22, and ram 18 is sealed to the outer surface of inner cylinder 12 and the inner surface of outer cylinder 14 by similar seals 22. An oil port 24 is let into the chamber between cylinders 12 and 14, and another oil port 26 is let into the chamber on the other side of piston 16. These ports 24 and 26 communicate respectively through oil lines 28 and 30 to a conventional 4-way valve 31, which is supplied with high pressure hydraulic oil from conventional pump means (not shown) through line 32 and is provided with a conventional oil return line 34. A conventional control device basing its actions on volume of oil pumped or other means which are not critical in the practice of this invention is shown diagramatically at 35 to operate 4-way valve 31 to supply high pressure oil successively to each side of piston 16 to cause reciprocal motion thereof, and to cause a predetermined length of travel each cycle of ram head 20 with respect to cylinder base 10.

Referring now also to FIG. 3, the ram head 20 is provided with a cruciform aperture 36 which acts as an upper guide to maintain a chain 38 in generally central alignment through the interior of cylinder 12. Ram head 20 is also provided with a transverse groove 40 in which rides upper bifurcated latch 42, this latch 42 being maintained in groove 40 by latch retainer plates 44 fixedly fastened to ram head 20 as by bolts 46. Latch 42 is provided preferably with a pair of opposed notches 48 (see FIGS. 2 and 3) forming a saddle in which a cross link of chain 38 may seat when latch 42 is moved inwardly to engage or support such link, the inward and outward motions of latch 42 in groove 40 being controlled by its connection by means of rod 50 to piston 52 off hydraulic cylinder 54.

Base is also provided with a cruciform-aperture 56 to act as a lower alignment guide for chain 38, and is also provided with a transverse groove 58 in which rides lower bifurcated latch 60 which in FIGS. 1 and 2 is shown with its notches 62 in latch 60 forming a saddle in which the bottom of another link of chain 38 may seat. Rod connection 64 to latch 60 is extended from hydraulic cylinder 66 so that piston 68 is in its inward position as shown, similar to the inwardposition of piston 52 of hydraulic cylinder 54.

Attached to ram head by bracket 70 is elongate square cross-section cam member 72 which is rotatable about its longitudinal axis, being maintained, however, in relative parallel alignment with outer cylinder 14 by means of a rotatable lock nut and screw combinations as at 74. Cam member 72 constitutes, as will be apparent, a side arm attached to ram head 20 and moving I with it, cooperating with a fixed member 76 which is attached to outer cylinder 14 and thus also to base 10. Fixed member 76 includes'or has attached thereto 'a plate 78 through which is rotatably mounted a bushing 80 having a circular outer edge and a square inner hole through which slidably passes cam element 72. At-

tached to housing 80 and rotating with it is indexingplate 82 having a pair of holes 84 spaced 90 apart and adapted to mate with one end of a ball lock pin 86 which passes through plate 78. Cam element 72 may thus be rotated 90 conveniently by actuation of handle 87 and can be indexed and locked in either of two positions 90 apart for either lift or lower mode. Also forming a part of fixed element 76, or attached thereto, are a pair of support members 88 diametrically opposed on either side of cam member 72 and on which are mounted 4-way hydraulic control valves 89 and 90 which are commercially available items each comprising the valve itself, its operating plunger and a cam follower roller as a unit as shown. The control valves 89 and 90 are arranged so that their follower rollers can engage the cam grooves in one pair of opposite sides of cam member 72 for lift mode operation of the jack, and when cam member 72 is turned 90 the rollers engage 'cam grooves on the other pair of opposite sides of cam with oil supply and return lines and 101; and 102 A and 103 respectively, these being connected to a conventional hydraulic pump or pumps (not shown) and supplied with oil under suitable pressure as will be apparent.

Details of cam member 72 will become clear from FIGS. 4, 5 and 6. As an example of cam grooves adapted for preferred operation according to this invention the cam element 72 in FIG. 4 is shown in lift position with 4-way valve roller 104 controlling the upper or ram head latch and roller 106 controlling the lower or base latch. In FIG. 6 are shown cross-over grooves 107 and 108 in which rollers 104 and 106 may travel laterally to place them in either the lift or lower cam groove set when cam element 72 is appropriately rotated by handle 87.

Operation of the embodiment of the chain jack illustrated and described above, will be described for lift mode with the chain carrying an assumed load ascending and moving progressively upward with respect to the base, and for the lower mode with the chain descending and moving progressively downward with respect to the base. I

A lift cycle of operation of the chain jack may be initiated with the 4-way valve rollers 104 and 106 in the positions shown in FIG. 4 and both latches 42 and 60- groove 110; lower latch 60 is free to disengage and retract in response to the preexistant signal generated by roller 106 rising out of groove 109, in cam member 72. After the chain has travelled about and preferably less than one half of a chain pitch the 4-way control valve 89 for the lower latch actuated by roller 106 engaging groove 112 biases the lower latch 60 so that it attempts to engage the chain 38 but cannot because a cross link is blocking. Shortly after lower latch 60 is biased to .engage, the upper latch 42 is biased to disengage chain 38 by roller 104 rising out of groove 110, but cannot do so because the force exerted by hydraulic cylinder 54 is not great enough to move it under load; each of hydraulic cylinders 54 and 66 exerts a bias force on its respective latch that is insufficient to move and disengage the latch from chain 38 when the chain load is supported by that latch. As soon as a proper window is presented to latch 60 it engages with chain 38 and at this time the ram extension is stopped and it is energized to retract by control 35. Actually, engagement and disengagement of latches 42 and 60 with chain 38 takes place slightly before the end of each stroke of ram 18. A slight amount ofover travel is provided in each ram stroke which is principally necessary in the down" mode of operation. The over-travel ensures that the ram travels a slight additional distance each time so that a latch already engaged with a chain link with the link seated in the saddle formed by notches 48 in latch 42 or by notches 62 in latch 60, will be moved a sufficient extra distance so that the latch and link will clear each other. When engaging, the latch is moved an appropriate distance to clear the link and allow proper seating in the saddle at commencement of the following stroke. The amount of the over-travel will be slightly greater than the depth of saddle notches 48 and 62. When ram 18 starts'to retract, lower latch 60 is in engaged position because roller 106 is in groove 112 of cam member 72 and upper latch 42 is still maintained engaged with chain 38 by the load, but is biased to disengage the chain by roller 104 now in disengage position on cam member 72. As soon as ram 18 has travelled a short retraction distance the load is transferred to lower latch 60 and upper latch 42 is free to retract and disengage. Thus the return stroke of ram 18 occurs with upper latch 42 disengaged and lower latch 60 engaged with chain 38 to support the load. Upper latch 42 remains disengaged and, at about half the ram travel again, roller 104 enters cam groove 110 to bias it to engage the chain 38. Shortly after this, when follower 106 rides out of groove 112 it biases lower latch 60 to disengage from chain 38. When the ram reaches the bottom end of its stroke, latch 42 finds a window and engages chain 38 (being previously biased to do so) and roller 106 enters cam groove 109 to cause latch 60 to engage chain 38 and temporarily hold the load until the cycle starts to repeat and upper latch 42 holds the load for a successive lift alternation. The situation is now as described for the beginning of the cycle which can be repeated to cause continuous travel by successive increments of the chain.

For the lower mode of operation, handle 87 is moved to a position-90 from that of FIG. 4, and, as will be seen in FIG. 5, presents the other set of cam grooves 114 and 116 for engagement by rollers 104 and 106. The rotated position of cam element 72 will be maintained by mating of ball lock pin with a 90 offset hole 84 in index plate 82.The action of the cam grooves and following rollers for the lower mode will be essentially reversed from those used for the lift mode, as will be readily apparent from FIG. 5, following the principles described in connection with the lift mode. Thus each retraction stroke of ram 18 will lower the load while upper latch 42 supports the load, lower latch 60 being disengaged; the load will be supported by lower latch 60 while ram 18 extends for another stroke with upper latch 42 disengaged.

It will be seen particularly from FIGS. 4 and 5 that the cam organization illustrated will bias a latch to enter a window between chain links at a position prior to the actual opening of the window. Thus in FIG. 4, for example, roller 106 will bias the lower latch to engage the chain by riding into groove 112 at a position when slightly less than one half the extending ram travel (and corresponding cam side arm travel) has taken place. However actual engagement, as explained heretofore, will take place at or near the end of the ram stroke to hold the load while the ram is being retracted, a slight amount of ram over-travel being necessary to allow a chain link to be clear of the saddles in the latches 42 and 60 as previously described. In like manner roller 104 will bias the upper latch to disengage by riding out of groove 110 at a position when slightly more than half the ram extension travel has taken place but actual disengagement does not take place until the load has been picked up by the lower latch. It will be noted that cam grooves 110 and 112 and also 114 and 116 overlap at the central part of cam member 72 in both lift and lower operation modes, and since these grooves are both arranged to produce a signal for latch engagement, there can be no position along the ram travel in objects along a horizontally placed chain. When the side arm cam element is placed in lift position the jack will automatically continue to lift, raising the chain or travelling up or along the chain in small increments which may be of the order of one or several pitches of the chain. When the side arm cam element is rotated to lower position the jack lowers the chain or travels down or along the chain in the reverse direction'in the same small increments. Accurate insertion of ram head and base latches is assured and the latch operating cams are arranged so that at least one latch will be engaged with the chain at all times, one latch being free to disengage only when the other latch is engaged with the chain. Complete safety of load support is thereby assured.

I claim:

l. A chain jack comprising a chain, and a base having a ram and a hydraulic cylinder for imparting reciprocal relative movement between said base and the head of said ram, latches movably attached to said baseand to the head of said ram, means for moving said latches in and out of engagement with said chain between links thereof, and means for synchronizing movement of said latches with said reciprocal relative movement between said base and said head of said ram to cause progressive relative movement between said chain and said base; in which the improvement comprises:

a. a side arm attached to said head of said ram;

b. a fixed member attached to said base;

0. one of said side arm and said fixed member provided with a pair of cams;

d. a pair of followers engagable with said cams mounted on the other of said side arm and said fixed member;

e. said followers being connected to hydraulic means for moving said latches in and out of engagement with .said chain at predetermined relative positions of said sidearm and said fixedr'nember.

2. A chain jack according to claim 1 in which said side arm is provided with a pair of cams in the form of grooves, one cam, on each of diametrically opposite sides of said side arm, said cams being engagable with a pair of followers mounted on said fixed member.

3. A chain jack according to claim 1 in which said side arm is provided with two pairs of said cams, each cam in each pair being on diametrically opposite sides of said side. arm, and a pair of followers for said cams mounted on said fixed member attached to said base, said side arm being attached to said head of said ram so as to be rotatable about its longitudinal axis thereby to bring a selected pair of said cams into engagement with said pair of followers for operation of said hydraulic means for moving said latches in and out of engagement with said chain for movement of said chain in one direction relative to said base, and to. bring the other pair of said cams into engagement with said pair of followers for operation of said hydraulic means for moving said latches in and out of engagement with said chain for movement of said chain in the other direction relative to said base.

4. A chain jack according to claim 1 in which the hydraulic means for moving said latches in and out of engagement with said chain is actuated by engagement of said followers with said cams to bias said latches to engage said chain between links thereof at positions prior to their alignment with a space between two aligned chain links.

5. A chain jack according to claim 1 in which the said hydraulic means for moving said latches in and out of engagement with said chain is actuated by engagement of said followers with said cams to release one of said latches from engagement with said chain only when the other of said latches is in engagement with said chain.

6. A chain jack according to claim 1 in which the said hydraulic means for moving said latches in and out of ram and the base of said cylinder. 

1. A chain jack comprising a chain, and a base having a ram and a hydraulic cylinder for imparting reciprocal relative movement between said base and the head of said ram, latches movably attached to said base and to the head of said ram, means for moving said latches in and out of engagement with said chain between links thereof, and means for synchronizing movement of said latches with said reciprocal relative movement between said base and said head of said ram to cause progressive relative movement between said chain and said base; in which the improvement comprises: a. a side arm attached to said head of said ram; b. a fixed member attached to said base; c. one of said side arm and said fixed member provided with a pair of cams; d. a pair of followers engagable with said cams mounted on the other of said side arm and said fixed member; e. said followers being connected to hydraulic means for moving said latches in and out of engagement with said chain at predetermined relative positions of said side arm and said fixed member.
 2. A chain jack according to claim 1 in which said side arm is provided with a pair of cams in the form of grooves, one cam on each of diametrically opposite sides of said side arm, said cams being engagable with a pair of followers mounted on said fixed member.
 3. A chain jack according to claim 1 in which said side arm is provided with two pairs of said cams, each cam in each pair being on diametrically opposite sides of said side arm, and a pair of followers for said cams mounted on said fixed member attached to said base, said side arm being attached to said head of said ram so as to be rotatable about its longitudinal axis thereby to bring a selected pair of said cams into engagement with said pair of followers for operation of said hydraulic means for moving said latches in and out of engagement with said chain for movement of said chain in one direction relative to said base, and to bring the other pair of said cams into engagement with said pair of followers for operation of said hydraulic means for moving said latches in and out of engagement with said chain for movement of said chain in the other direction relative to said base.
 4. A chain jack according to claim 1 in which the hydraulic means for moving said latches in and out of engagement with said chain is actuated by engagement of said followers with said cams to bias said latches to engage said chain between links thereof at positions prior to their alignment with a space between two aligned chain links.
 5. A chain jack according to claim 1 in which the said hydraulic means for moving said latches in and out of engagement with said chain is actuated by engagement of said followers with said cams to release one of said latches from engagement with said chain only when the other of said latches is in engagement with said chain.
 6. A chain jack according to claim 1 in which the said hydraulic means for moving said latches in and out of engagement with said chain exerts a force insufficient to move one of said latches when said latch is engaged with said chain and the chain load is supported by said latch.
 7. A chain jack according to claim 1 in which said ram and said hydraulic cylinder are hollow and said chain passes through said hollow ram and hollow cylinder being centrally aligned in said hollow ram and hollow cylinder by cruciform apertures in the head of said ram and the base of said cylinder. 